In recent years, most of the products that are commercially available as the fiber-use softener have a composition containing quaternary ammonium salt having two long-chain alkyl groups in each molecule, as typically represented by di(long-chain alkyl)dimethyl ammonium chloride. However, the quaternary ammonium salt of this type has a problem in which, when its residual substances after use are discharged into the natural field, most of them are accumulated without being subjected to biodegradation.
In order to solve this problem, N-methyl-N,N-bis(long-chain alkanoyl oxyethyl)-N-(2-hydroxyethyl) ammonium methylsulfate or the like has been introduced to the market as modified products. In comparison with the above-mentioned quaternary ammonium salt, this product has better biodegradability.
N-methyl-N,N-bis(long-chain alkanoyl oxyethyl)-N-(2-hydroxyethyl) ammonium methylsulfate is prepared by esterifying triethanol amine using a long-chain fatty acid and successively quaternizing this by dimethyl sulfate. The reaction molar ratio of fatty acid to triethanol amine is normally set to 1.8 to 2.1, and in this case, the ratio of diester quaternary salt to the total amount of monoester quaternary salt, diester quaternary salt and triester quaternary salt is 43 to 47 weight %. The reaction molar ratio is set to 1.8 to 2.1 because at this time, the ratio of diester quaternary salt is maximized, and the reaction molar ratio smaller than 1.8 or greater than 2.1 causes a reduction in the ratio of diester quaternary salt, resulting in degradation in the softening performance. However, even when the reaction molar ratio is set within 1.8 to 2.1, it is not necessarily possible to provide a sufficient softening property.
In order to solve the above-mentioned problem, WO9742279 has disclosed quaternary ammonium salt in which the ratio of diester quaternary salt is not less than 55 weight % with the ratio of triester quaternary salt being set to not more than 25 weight %, and the preparation method thereof. Although this product has an improved softening performance, it has not been a satisfactory product.
Most of the other softener base agents have the di-long-chain alkyl quaternary ammonium salt structure, and with respect to tri-long-chain alkyl quaternary ammonium salt, the application thereof as a softener base agent has not been proposed because of the reasons that more hydrophilic groups exist in comparison with lipophilic groups with insufficient dispersing property to water with the result that the softening performance is not sufficiently exerted.
Moreover, such quaternary ammonium salt is prepared by allowing the corresponding tertiary ammine to react with a quaternizing agent and at the time of the quaternizing reaction, alcohol solvents such as isopropyl alcohol and ethanol are generally used. However, alcohol based solvents have a low flash point which causes a risk of a fire, and also have inherent odor causing adverse effects on odor of the products containing these base agents, and these do not function as effective components for softening cloth and hair, etc., resulting in the corresponding additional costs. However, without the application of such a solvent, the melting point of quaternary ammonium salt becomes higher, resulting in another problem with handling.
The objective of the present invention is to provide a softener composition which contains tri-long-chain alkyl quaternary ammonium salt that has been considered to be difficult to use as a softener base agent, and which provides a sufficient softening performance.
EP-A675941 and WO97/42279 disclose a mixture of quaternary ammonium salts including 50% or more of a triester-having quaternary ammonium salt.
WO01/32813 and JP-A 2001-131871 disclose a mixture of quaternary ammonium salts including 15 to 85% of a tri-ester-having quaternary ammonium salt, up to 40% of a di-ester-having quaternary ammonium salt and 15 to 85 of a mono-ester-having quaternary ammonium salt for a for a softener. DE-A 1935499 discloses production of a tri-ester-having quaternary ammonium for softener, in Example 2.